This invention relates to sewing machines capable of stitching laterally and, more particularly, this invention relates to mechanisms for moving a sewing machine feed dog in a lateral direction.
As one example of a mechanism for moving a feed dog laterally, FIG. 2 is a drawing copied from Japanese laid open Pat. No. 62-201182, published on Sept. 4, 1987, and assigned to Juki Corporation, the same assignee as that of the present application.
Referring to FIG. 2, when a hook drive shaft 1 completes one rotation, an eccentric cam 2 causes an arm 3 to conduct one up-and-down motion. An end 3a of the arm 3 conducts one up-and-down motion and causes a shaft 4 to move up and down. A roller 5, pivoted to the end of shaft 4, also conducts one up-and-down motion and causes a feed bracket 6 to move up and down and resultantly a feed dog 7 moves up and down. Also, when shaft 1 completes one rotation, an eccentric cam 9 causes a bifurcated-arm 10 to move up and down.
A feed-adjusting motor 11 causes a forward-feed adjuster 12 to change its degree of inclination such that a slide block 13, slidably inserted in a groove 12a, causes the bifurcated arm 10 to move in a direction perpendicular to the shaft 1 and causes a shaft 14 to swing. Accordingly, the feed bracket 6 moves back and forth, the feed dog 7 feeds back and forth, and thus a work fabric placed on the feed dog 7 is fed forward.
When a lateral-feed-adjusting motor 15 rotates, a lateral mover 19 is slid laterally along a shaft 20 by a link 17 and a link arm 16. As the lateral mover 19 moves laterally, a contactor 21 located at the end of the lateral mover 19 contacts with a left-feed cam 22, with a straight-feed cam 23, or with a right-feed cam 24. The left-feed cam 22 and the right-feed cam 24 are eccentric cams and the straight-feed cam 23 is a circular cam. These cams are fixed to the shaft 1. When the contactor 21 contacts with the left-feed cam 22 or the right-feed cam 24, the eccentricity of these cams 22, 24 cause the lateral mover 19 to rock about the shaft 20.
A bifurcated plate 19a projected perpendicularly from the lateral mover 19 provides a slit 19b in which a shaft 25, projected perpendicularly from the shaft 20, is loosely inserted. The shaft 25 provides a roller cam 27 at its end. The roller cam 27 is in contact with a sloped surface 26a of a sloped surface cam 26. Thereby, as the lateral mover 19 rocks about the shaft 20, the roller cam 27 rolls on the sloped surface 26a. Since the sloped surface 26a is stationary, the shaft 20 is moved laterally.
Accordingly, a rotary arm 28 slidably mounted on the shaft 20 is moved laterally, by collars 20b, 20c fixed to the shaft 20 as shown in FIG. 2A, so that the feed bracket 6 with the feed dog 7 fixed thereon moves laterally. When the contactor 21 contacts with a circular cam 23, the lateral mover 19 does not rock, the shaft is not moved, and the workpiece is only fed straight. As shown in FIG. 2A, the end 20a of the shaft 20 is pressed by a plate spring PS such that the roller cam 27 always contacts the sloped surface cam 26.
According to the above example, as shown in FIG. 2, the shaft 20 extends from the sloped surface cam 26 to the plate spring PS, so that its total length is very long. Thereby, the problem of bending moments on, and deflection of, the shaft 20 is unavoidable. Additionally, such a long shaft is inconvenient so far as positioning of other mechanical parts is concerned.